Fuel and ignition control



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H. T. JARvls `FUEL AND IGNITION CONTROL Filed June 25, 1945 Ilm .NMRN

. engines.

Patented Nov.l 2, 1948 v FUEL AND IGNITION CONTROL llarold'l. Jarvis, Manchester, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application June 25, 1945, Serial No. 601,438

is claims. (ci. 12s-117) This invention relates to the control of fuel andV ignition systems for engines, particularly aircraft This application is a continuation-inpart of co-pending Jarvis application Serial No. 481,114, filed March 30, l1943, now Patent No. 2,380,967, assigned to .applicants assignee.

" An object of this invention is to provide improved means for regulating the mixture strength of an engine.

Another object is to provide means for correlating the ignition timing and the charge mixture strength of an engine.v

Another object is to provide improvements in fuel and ignition control systems for internal combustion engines.

A further object is to provide a novel control device, particularly for internal combustion aircraft engines. l

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawing which illustrates what is now considered to be a preferred embodiment of the invention.

In the drawing,1'\ig. 1 is a schematic view showing a fuel and ignition control apparatus constructed according to the teaching of this invention.

Fig. 2 shows schematically fuel-air ratio curves such as may be obtained with the control apparatus of Fig. l.

The embodiment of the invention shown in the drawing is particularly adapted for use with air- I, craft engines having engine driven superchargers, but it is to be understood that the invention is not limited to such use.

Charge mixture strength, or Afuel-air weight ratio, of an engine must be accurately controlled throughout the engine operating range in order to obtain maximum emciency and fuel economy and other desirable engine operating characteristics. Spark advance, or the time at which ignition occurs with respect tol piston position in a reciproeating internal combustion engine, must also be accurately controlled for the same reasons. For best results, the operation of these two controls should be correlated. An adjustment of either may affect engine operating characteristics such as the rate of burning of the charge, detonation, power output, fuel economy and engine temperatuie and therefore may require a corresponding adjustment of the other control to obtain optimum operating characteristics. Spark advance is usually expressed by the number of degrees of crankshaft rotation at which the spark plugs are red before the piston reaches top dead center.

Mixture strength is usually expressed in pounds of fuel (such as gasoline) per pound of air in the engine charge.

According to this invention, both mixture strength and spark advance maybe automatically of which is shown at i1, is supplied with charg-A ing fluid 4(air or air and fuel) through induction pipes, one of which is shown at I6, by a main stage supercharger impeller l2 mounted in a supercharger or blower case, a portion of which is shown at I0. The impeller is splined at i3 to a shaft l 5 driven in a known manner by the engine crankshaft (not shown) through a speed increasing gear train or transmission (not shown) which may, for instance, be similar to ,those disclosed and claimed in Hobbs Patent No. 2,323,601, dated July 6, 1943 and in Hobbs-Willgoos application, Serial No. 492,423, now Patent No.2,400,307, filed June 26, 1943, assigned to applicants assignee.

Intake air is supplied to the supercharger :inlet or throat i4 by a manifold 22 connected either directly to a scoop or ram positioned in the free airstream flowing over the aircraft or to the outlet of an auxiliary supercharger stage. 'I'he rate of flow by weight of intake air, and therefore engine power output, is controlled by throttle 2li.

Air passing to the engine is measured by carburetor metering section 26 comprising. main venturi 30, auxiliary venturi 30' and impact tubes 36, which cooperate to produce throat and scoop pressures in chambers l0 and'38, respectively.

These pressures, as corrected for variations in density by altitude compensator 32, are admitted to chambers 21, 29 on opposite sides of air diaphragm 28. The resultant force exerted by the diaphragm on fuel flow regulating valve 52 is a function of the rate of flow by weight of intake air and urges the valve toward open position.

Fuel is supplied to valve 52 by pump 06 :from tank t2 through line 4' l and strainer 50. A vapor trap including floatv valvellB may be provided to eliminate gases from the liquid fuel, which is prei'- erably gasoline.

Fuel in an amount controlled by valve 52 iioWs through unmetered fuel chamber 54 and line 58 4 to the fuel control body or metering jet section 58. After being metered in control body 58, the fuel passes through the metered fuel line 68 to the fuel' discharge valve E85 and then into the fuel spinner |54 which sprays it into the air entering the vaned passages of impeller I2.

jets between the unmetered and metered lines 56, 68 which is proportional to the compensated air pressure drop between the throat chamber 48 and the scoop chamber 38, thus regulating the rate of flow by weight of fuel to the engine in predetermined ratio to the rate of flow by weight of engine intake air, throughout the engine operating range.l

This fuel-air ratio may be varied by controlling the jets in the fuel control Ibody 58. The basic fuel-air ratio throughout the engine operating range is established by the main or cruise jet 66, which is continuously open. In addition to the flow through this jet, fuel may also flow from the unmetered jet chamber |56 through the economizer jet 18 into the chamber 14 and then through the auto-rich jet 16 into the metered jet chamber |51.. when the auto-rich valve 11 is open as shown in Fig. 1. Jet 16 has a greater restriction than jet 18. Therefore, assuming valve 88 to be closed, the mixture is enriched by an amount determined substantially by the size of jet 16 when valve 11 is open.

It is desirable under high engine power output conditions to provide additional enrichment or higher mixture strengths toprevent detonation, and for other purposes. This is accomplished r by economizer valve 88 operated by diaphragm 84 subjected to metered fuel pressure through passage 85 and unmetercd fuel pressure through line 86. When the fuel pressure drop becomes suiliciently high, valve 88 is opened against the force of spring 88 to provide .additional fuel in an amount determined by the value of the fuel pressure drop, the rate of spring 88 and the contour of valve 88, up to a maximum quantity determined by the size of economizer jet 18, which imposes a limit on the maximum flow permitted through both valve 88 and jet 16. Fuel enrichment occurs regardless of whether or not the carburetor is in the auto-rich position ,in which valve 11 is open, or in the auto-lean position in which valve 11 closes the opening 19 and thereby shuts o'ff the flow of fuel through jet 16.

Idle valve linked in a known manner with the throttle 24, is moved to a metering position, in which it restricts the flow from the end of unmetered fue] line 56 and thereby controls the mixture strength, when the throttle is closed and the engine is idling. When the throttle is open, idle valve 5| has no appreciable effect on the mixture strength.

According to the present invention, the above described fuel control apparatus, which is more fully disclosed in Palmer application Serial No. 529,104, filed April 1, 1944, assigned to applicant's assignee, is modified and correlated with the engine ignition control apparatus as follows.

An extra lean metering jet 48|, controlled by a two-position auto-lean valve unit 408, is supplied with unmetered fuel from line 56 by passage 2||. Fuel passing through jet; 48| flows to metered fuel line 68 through passage 2|8, and from line 68 to the engine. Such flow through the super or extra lean jet 40| is controlled by valve 486. Flow through supplemental or auxiliary jet 48|, when valve 486 is open. supplements flow through the metering jets in control body 58, to establish normal fuel-air ratios. When valve 486 closes, flow through jet 40| is cut-off and the normal mixture strength will be decreased by an amount determined by the fiow capacity of jet 48|.

Valve 406 is biased to closed position by a spring 289 and is opened by a predetermined pres sure difference between the unmetered and metered fuel lines 56, 68. is attached to the valve actuating diaphragm |86, which cooperates with the partition 4|2' and the wall 4|4 to form uid tight chambers on opposite sides of the diaphragm. These chambers are subjected to metered and unmetered fuel pressures in lines 68, 56 by passages 2|8, 2||, respectively. Diaphragm |86 actuates the fuel valve 486 and also actuates the by-pass or bleed valve |98 of the ignition system. Valve |98 is held in closed position by spring 201. This spring is preferably considerably weaker than the diaphragm spring 289 and serves merely to hold the stem of valve |98 in abutment with the diaphragm. When the pressure difference between fuel lines 56, 68 becomes sumciently large, diaphragm |86'overcomes the force of spring 289 and moves upwardly to lift fuel valve 406 from its seat. The diaphragm in its upward movement also contacts the stem of valve |90 and opens this valve against the force of spring 281. Seals (or sealing diaphragms) may be provided if desired at the place where the stem of valve |98 passes through the partition 4|2.

The engine ignition system comprises magnetos |4, |6' which supply ignition current at timed intervals to spark plugs |1' of the engine cylinders I1. The magnetos are driven from the engine crankshaft by gear trains including magneto drive gears |89, ||8 in a manner more fully disclosed in Jarvis application Serial No. 481,114, filed March 30, 1943, to which reference is made for a more complete disclosure of the basic ignition system referred to herein.

For changing the timing of the magnetos, or the time at which ignition current is supplied to the spark plugs with respect to piston position, the magneto gear trains are each provided with bevel idlerv gears |84, |86 mounted on cages |88- rotatably supported on the magneto shafts |80, to which gears |89, ||8 are fixed. Cages |08 are connected by arms |34, |36 to a cross bar or link |32 attached to the piston |24 of a servo motor |8|. When pressure fluid such as oil is admitted to one or the other of cylinders |26, |28 of the Valve |62 is actuated by diaphragm |12 sub- The stem of valve 485 jected to the pressure difference between fluid lines |14, |16, which are respectively connected through restriction |98 to the blower outlet and through restriction 2001to the blower inlet. Thus the chamber portion of the spark advance operating unit is divided by diaphragm |1-2 into two iluidtight chambers connected -to blower throat and blower rim. y

A spring |18 maintains valve |62 in its downward or retard position, determined by the stop |63. When the 'force exerted by the uid pressures on diaphragm |12 is sufficient to overcome the force of spring |18, valve |62 is moved upwardly to its advance position, determined by the abutment of the stop |65 against chamber |10.

Under some conditions it is desirable to maintain the spark retarded even when the supercharger pressure rise is 'suiciently high to hold valve |62 in its upper or advance position. -For this purpose by-passvalves |90 and 50| are pro vided. When either of these valves is opened, the effect is to bleed or by-pass air from the blower rim line |14 to the blower throat'line |16. Restrictions |96, 200 are made of such value in relation to ythe size of valves |90, 50| that the open- -ing-of either of these valves will approximately equalize the pressure in lines |14, |16, thereby disabling the ignition timing mechanism, or rendering it ineffective to advance the spark, by causing the pressures on opposite sides of the diaphragm in chamber |10 to become substantially equalized and enabling spring |18 .to maintain or return valve |62 -to the retard position.

By-pass valve |90 of the spark advance control unit 202 is Acontrolled by fuel head diaphragm |86. The force exerted by this diaphragm on the valve is determined by the fuel pressure drop which is in turn determined by the rate of flow by weight of engine intake air. Consequently diaphragm |86 will open valve |90 against the force of springs 209, 201 when intake airflow (and engine power output) reaches a predetermined value. Fuel valve 406 will of course lbe opened and closed simultaneously with ignition valve |90.

By-pass valve 50| in the mixture control 500 is actuated by handle 502. When the handle is moved to change the mixture setting of the carburetor, shaft 5|4, fixed thereto, is rotated to angularly adjust yoke 503 connected to valve lever 505, thereby shifting valve 11 to close or open the port 19. Movement of shaft 5|4 also angularly shifts a cam 5|6, keyed to the shaft, to close or open'bleed valve 50| against the force of spring 501 .by means of bell crank 508, fulcrumed at 5I0. The levers and cam are so arranged that whenever handle 502 is in the auto-rich position valves 11A As the throttle 24 is moved from idle position to the full open position the rate of intake airflow increases and the mixture streng-th and ignition timing are varied, for example as shown in Fig. 2.

As schematically shown inthe upper (or autorich) curve of Fig. 2, with an auto-rich mixture setting (valve 11 open) the mixture strength decreases along the downwardly sloping line at the left of the curve from a rich idling mixture to a cruise mixture strength determined bythe size of jets y|56 and 16. The fuel-air ratio is then maintained substantially constant through a portion of the cruising power range during which valve 406 is closed, as shown by theleft hand horizontal portion of the curve. When the rate of intake airflow reaches -a predetermined v alue, which may be selected by spring 209, the fuel metering head becomes large enough to force diaphragm |86 upwardly, lifting valve 406 to increase the mixture strength as indicated by the upward step in the curve. The mixture strength will then again .be held constant at the higher value, determined by the size of jets 66, 16 and 40|, as shown by the right hand horizontal portion of the curve. It is further increased by the opening of economizer valve 80.when the power output enters `the high or full power range, and 4the mixture is gradually enriched, as shown by 4the upwardly sloping line at the right of the curve, in accordance with each increase in power output beyond the cruising range. Because of the economizer or limiting j et 10, the fuel-air curve flattens out .to a substantially constant value, as shown at the extreme upper right hand portion of the curve, when the engine approaches maximum power output.

Under auto-rich mixture conditions valve 150| is open and the ypressures in lines |14, |16 are thereby equalized, enabling spring |18 to maintain the ignition timing in the normal or retard position regardless of variations in intake airflow, 4power output, or mixture strength.

With an auto-lean mixture setting (valve 11 closed) the fuel-air ratio follows the lower (or auto-lean) curve schematically shown in Fig. 2. The fuel-air ratio decreases as indicated by the sloping line at the left of the curve until the engine power output enters ,the cruising range. It then remains approximately constant at a value de-4 termined by the size of jet 66 through the major part of the range labeled super auto-lean," during which valve 406 is held closed by spring 209. When the rate of intake airflow increases to a f value sufficient .to open valve406 the mixture is enriched in an amount determined by the size of 40| until economizer Valve 80 is openedto enrich.

the mixture in the high power range, as described above in connection with the auto-rich curve.

Valve 50| is closed when the valve 11 is closed and therefore the ignition timing will be advanced (for instance from 25 B. C. T. normal to 37 B. T;

C. cruising spark advance position) when .the mixture setting is auto-lean and the supercharger pressure rise becomes large `enough to overcome the force of spring |18. An increase in intake airflow (and consequently engine power) also results Vin an increase in the pressure rise across the supercharger. When the pressure rise reaches a predetermined value (for instance about 3" Hg is suitable in some installations and about 8" Hg for some other installations) diaphragm |12 is forced upwardly to advance the ignition timing.

In Fig. 2 the point at which the blower pressure ,rise becomes sulcient to compress spring |13 and shift thetiming to 4the advance position has been placed, for illustration, at the beginning of the cruising power range.- 'Ihe point at which the fuel metering head `becomes suilicient to compress the spring 209 has been placed near the upper end ofthe cruising power range. With such an arrangement, .the engine is operated with the spark retarded in-the idling power range, with spark ad-A vanced in the super or extra-lean cruising range (valves |00, 406 closed) and with spark. retarded in the lean cruise range (valves |90, 406 open) and the high power range (valve 80 partially or fully open). Thus the ignition timing and mixture strength may be automatically regulated, one in accordance with the other, when the mixture setting is auto-lean. With an auto-rich mixture setting, the ignition timing is maintained in the retard position and the fuel-air ratio is controlled independently of spark advance.

When the throttle is returned from the full open to the idle position the events described above will occur in reverse order, though preferably at slightly different values of intake airflow. Valves |90 and 406 may be so designed that the pressure differential across them tends to hold them closed, thereby insuring their shift to fully open position as soon as they are cracked" or partially opened and preventing hunting In other words, the valves may be designed if desired -to provide a hysteresis effect, so as to close only when the airflow decreases slightly below the value required to open the valves.

This invention may be used with the water injection apparatus of Palmer application Serial No. 529,104, referred to above, or with fuel injection systems in which the fuel is directly injected into the engine combustion chamber or chambers. The invention, of cour-se, is not limited to the speciflc embodiment herein illustrated and described, l

but may be used in other ways without departure from its spirit as defined by the following claims.

Anormal fuel-air ratios, fluid pressure responsive means for actuating said controlling means to fully open said supplemental jet at al predetermined point within the intermediate portion of the engine power output range, and an engine control device actuated by said fluid pressure responsive means.

2. Engine fuel supply apparatus comprising at least two fuel metering devices, means for maintaining a controlled fuel pressure drop across said metering devices, a first valve responsive to said fuel pressure drop for controlling the flow of fuel through one of said devices, a. second valve responsive to said fuel pressure drop for controlling the flow of fuel through the other of said devices, and means operatively associated with one of said valves for correlating the operation of an engine control device with the operation of said `one valve.

3. The apparatu-s of claim 2, in which one of said valves is opened in response to an increase in `said fuel pressure drop .to a first predetermined value and the other of said valves is opened in response to a further increase in said fuel pressure drop to a second predetermined value.

`it In an engine, a pressure or injection type carburetor having economizer means, an extralean metering means separate from said economizer mea-ns, a rst valve for controlling the flow of fuel `through said extra-lean metering means, a. second valve for regulating the operation of an engine control device, and means for simultaneously actuating said valves. 'f 5..,The combination of claim 4, in which said means therein, addi-tional metering means subjected to said fuel pressure differential and actuated in accordance. with variations in said fuel f pressure differential, and engine control means operatively associated with said additional metering means.

y'7. In an aircraft engine, adjustable means for varying the charge mixture strength of said engine, and means responsive to variations in engine intake airflow and operatively associated with the ignition system of said engine for adjusting said adjustable means.

8. Engine ignition and fuel supply apparatus comprising, spark advancing means, fuel control means, and means for automatically disabling said spark advancing means in accordance with an operation of said fuel control means.

9. In an ignition and fuel control apparatus for an engine, a first valve for varying the ignition timing of said engine, a second valve for varying the charge mixture strength of said engine, and means for simultaneously actuating both of said valves in accordance with variations in engine intake airflow.

l0. In an aircraft engine, an adjustable ignition timing device, an adjustable fuel-air ra-tio control device, and automatically operative means movable in one direction to simultaneously retard said ignition timing and increase said mixture strength and movable in another direction to simultaneously advance said ignition timing and decrease said mixture strength.

11. In an aircraft engine having a supercharger and having a supercharger rise actuated ignition timing mechanism and a fuel-air ratio control device, means for modifying the effect of said supercharger pressure rise upon said ignition timing mechanism, means for modifying the fuel-air ratio established by said control device, and autoy matically operative means for controlling said supercharger rise modifying means and said fuelair ratio modifying means.

12. The apparatus of claim 11, in which said fuel-air ratio modifying means and said supercharger rise modifying means are controlled in accordance with variations in a fluid pressure differential that varies with variations in engine intake airflow.

13. In an aircraft engine having a supercharger, an ignition timing device, fluid passage means connected through fluid ilow restrictions with the inlet and the outlet of said supercharger for actuating said ignition timing device, means for measuring the rate of intake airilow to said supercharger, a throttle valve between said airflow measuring means and said supercharger, means operatively associated with said airflow measuring means for establishing a fuel pressure differential which is a measure of the rate of intake airflow, means subjected to said fuel pressure differential for controlling the flow of fuel to said engine in predetermined relation to the flow of intake air, manually operated valve means for regulating said predetermined relation of fuel flow to air flow,

i 9" ignition timing control duid passage means and with said manually operated valve means, ignition ,timingcontrol means connected with -said iiuid passage means and with a diaphragm actuated-by said fuel pressure differential, and a fuel fiow control valve connected with said diaphragm.

14. In a method oi operating an aircraft engine having fuel control means provided with rich and lean mixture settings, the steps of, regulating the mixture strength of the engine charge independently of the ignition timing of said engine during operation in said rich mixturesetting, and simultaneously varying the mixture strength oi the engine charge and the ignition timing of said engine during operation in said lean mixtur setting.

'15. In an ignition and fuel control apparatus for an engine, a rst valve for varying the ignition timing of said engine, -a second valve for varying i `the charge mixture strength 4of said engine, and

pressure responsive means for4 simultaneously actuating both of .said valves, said pressure responsive means being subjected to a fluid pres sure diiieren'tial which is a measure of the rate of iiow by weight of engine intake air.

means connected with said simultaneously retard said ignition timing and in- 1 16. In an aircraft engine, an adjustable ignition timing device, an adjustable fuel-air ratio control device, means movable in one direction to crease said mixture strength and movable in -another direction to simultaneously advance said ignition timing anddecrease said mixture strength, and means for rendering said movable means ineffective to advance said timing under 'predetermined' engine operating conditions.

Y HAROLD T.JARVIS.

` REFERENCES CITED The following references areV of record in the file of this patent: y 4

UNITED STATES PATENTS Number Name Date Re. 22,447 Hersey Feb. 29, 1944 2,217,364 Halford et a1 Oct-8, 1940 2,309,226' Ud-ale Ja'n. 26, 1943 2,361,227 Mock Oct. 24, 1944 2,361,228 Mock Oct. 24, 1944 2,372,356. Chandler .l '..i Mar, 27, 1945 2,394,664

Chandler Feb. 12, 1946 

